Lamps for generating near infrared or infrared radiation find wide application in many analytical instruments such as spectrophotometers, attenuated total reflectance (ATR) spectrophotometers and near infrared diffuse reflectance spectrometers of the kind shown in patent application Ser. No. 15,017, filed: Feb. 26, 1979, assigned to a common assignee.
Incandescent lamps having a tungsten filament bulb are most often used as a source of near infrared radiation in such reflectance analysis instruments. The major drawback in using these incandescent lamps is that the tungsten filament has a very low emissivity in the near infrared range. Therefore, such lamps have poor radiation output. In addition, their visible emission is high contributing undesirable stray light, while increasing power consumption and heat loading for the lamp. In order to compensate for these problems, the lamp is usually operated at a lower filament temperature. However, the lower filament temperature causes a further loss in the radiation output of the lamp.
In order to provide a beam of monochromatic radiation for the near infrared diffuse reflectance spectrometer, the output of the lamp must be further filtered and collimated, thus reducing the intensity of the radiation still further.
Therefore, it would be desirable to produce a lamp for spectrophotometers and similar instruments which can provide a beam of radiation of greater radiance than is presently available using the same or less power consumption.